An organic compound A upon reacting with $NH_3$ gives B. On heating B gives C. C in presence of $KOH$ reacts with $Br_2$ to give $CH_3CH_2NH_2$ A is :

Question

$ (a)\;CH_3CH_2CH_2COOH \\ (b)\;H_3C-CH-COOH \\ (c)\;CH_3CH_2COOH \\ (d)\;CH_3COOH $